PROJECT SUMMARY Overutilization is increasingly viewed within the framework of patient safety. In primary care, patients with acute low back pain frequently request diagnostic imaging, and primary care physicians (PCPs) feel pressure to acquiesce to such requests to sustain patient trust and satisfaction. Spinal imaging in patients with acute low back pain poses risks from diagnostic evaluation of false-positive findings, patient labeling and anxiety, and unnecessary treatment (including spinal surgery) with potential downstream complications. Watchful waiting advice has been found an effective strategy to reduce low-value treatment (e.g., pediatric ear infections), and some evidence suggests a watchful waiting approach would be acceptable to many patients requesting tests. Meanwhile, psychological theory (regulatory fit vs. non-fit) suggests that physician messages could be tailored to magnify patient acceptance of a watchful waiting strategy. In response to the Agency Healthcare Quality and Research's interest in advancing simulation research to improve patient safety, we propose to refine and evaluate a novel simulated intervention using standardized patients (SPs) -- or actors playing the roles of patients ? to teach PCPs to endorse a watchful waiting approach when patients request low-value spinal imaging for low back pain. Specific aims are: Aim 1: To use key informant interviews of front-line PCPs and focus groups with primary care patients to refine a theory-informed standardized patient-based intervention designed to teach practicing PCPs how to advise watchful waiting when patients request low-value spinal imaging for low back pain. Aim 2: To test the effectiveness of standardized patient instructor (SPI)-delivered PCP training in the use of watchful waiting in a randomized clinical trial. We hypothesize that the intervention will: a) reduce rates of low-value spinal imaging among actual patients with acute back pain seen by PCPs post-intervention (adjusting for pre-RCT rates); b) increase PCP advice to pursue watchful waiting during a followup visit with a previously unseen SP; c) increase PCP self- reported use and efficacy of advising watchful waiting with actual low back pain patients; and d) have no adverse impact on actual patient trust and satisfaction with physicians. Aim 3: To assess whether the intervention effects generalize to other high-cost, low-value imaging tests. We hypothesize that the SP intervention will: a) decrease rates of advanced neck imaging among actual patients with neck pain seen by study PCPs during the follow-up period (adjusting for baseline rates), and b) increase PCP self-reported use and efficacy of advising watchful waiting rather than imaging for patients with neck pain and other musculoskeletal pain.